不同放射剂量下大鼠视网膜组织形态与氧化应激因子的变化

目的　通过直线加速器照射大鼠眼部制作放射性视网膜病变大鼠模型，观察大鼠视网膜组织形态与氧化应激因子的变化。方法　选取４５只２个月龄ＳＤ大鼠，随机分为正常对照组、１０Ｇｙ组、３０Ｇｙ组，每组１５只。直线加速器照射眼部，单次剂量１０Ｇｙ。１０Ｇｙ组放射１次。３０Ｇｙ组每周放射１次，连续３周，合计剂量３０Ｇｙ。放射后正常饲养３个月，处死各组大鼠并取眼球。采用ＨＥ染色观察视网膜组织形态，黄嘌呤法测视网膜超氧化物歧化酶（ｓｕｐｅｒｏｘｉｄｅｄｉｓｍｕｔａｓｅ，ＳＯＤ）活性、丙二醛（ｍａｌｏｎａｌｄｅｈｙｄｅ，ＭＤＡ）含量以及ＥＬＩＳＡ法测定活性氧自由基（ｒｅａｃｔｉｖｅｏｘｙｇｅｎｓｐｅｃｉｅｓ，ＲＯＳ）含量。结果　造模后３个月，３０Ｇｙ组视网膜各层组织结构松散，神经节细胞层及内核层水肿，１０Ｇｙ组模型大鼠视网膜仅神经节细胞层轻微水肿。与正常对照组相比，１０Ｇｙ组ＳＯＤ活性、ＭＤＡ及ＲＯＳ含量分别为（８８．８０±１６．４４）Ｕ·ｍｇｐｒｏｔ－１（Ｐ＜０．０５）、（１１．０２±４．０２）ｎｍｏｌ·ｍｇｐｒｏｔ－１（Ｐ＜０．０１）、（１６．８９±６．０２）Ｕ·ｍＬ－１（Ｐ＜０．０５），差异均有统计学意义；３０Ｇｙ组ＳＯＤ活性、ＭＤＡ及ＲＯＳ含量分别为（７８．５０±１８．０９）Ｕ·ｍｇｐｒｏｔ－１、（１５．２６±５．３４）ｎｍｏｌ·ｍｇｐｒｏｔ－１、（２８．６６±８．８２）Ｕ·ｍＬ－１，三者差异均有显著统计学意义（均为Ｐ＜０．０１）。与１０Ｇｙ组比较，３０Ｇｙ组ＭＤＡ含量和ＲＯＳ含量均升高（均为Ｐ＜０．０５）。结论　直线加速器放射造模时，３０Ｇｙ为最佳放射造模剂量，造模后大鼠视网膜ＳＯＤ活性降低，ＭＡＤ及ＲＯＳ含量均升高，可能是放射性视网膜病变的发病基础。

Changes of retinal morphology and oxidative stress factors under different radiation doses in rats

Objective To explore methods of basic study on radiation retinopathy by observrng morphology in retinal tissue and oxidative stress of radiation retinopathy of rats model.which eyes radiated by linear accelerator. Methods Forty-five SD rats ( aged 2 months) were randomly divided int0 3 groups : Control group , 10 Gy group , 30 Gy group , 15 cases in each group. The rats of experimental groups were radiated by the linear accelerator with the single dose of 10 Gy. 10 Gy group rats were radiated once. 30 Gy group was radiated once a week for 3 weeks.so the total dose was 30 Gy in all. The rats were killed and removed the eyes after radiated 3 months. The changes of morphology in retinal tissue was observed with HE staining, superoxide dismutase ( SOD) activity and malonaldehyde ( MDA) content were detected by Xanthine method. and reactive oxygen species ( ROS) content was measured with ELISA. And the differences were analyzed between groups. Results After radiated 3 months, compared with the control group, HE staining in 30 Gy group displayed that the retinal structure was loose , the ganglion cell layer and inner nuclear layer were edema , and it was edema only in the ganglion cell layer of 10 Gy group. Compared with the control group , SOD activity was ( 88. 80 + 16. 44 ) U . mgprot ’i ( P < 0. 05 ) , MDA content was ( 11. 02 + 4. 02 ) nmol . mgprot -i (P < 0. 01) .ROS content was ( 16. 89 +6. 02 ) U . mL -l (P < 0. 05 ) in 10 Gy group ; In 30 Gy group , SOD activity was ( 78. 50 + 18. 09 ) U . mgprot ’i , MDA content was ( 15. 26 +5. 34 ) nmol . mgprot ’i , ROS content was ( 28. 66 + 8. 89 ) U . mL l , there was significant statistical difference in these indexes ( all P < 0. 01 ) . And compared with 10 Gy group,MDA and ROS contents were all increased in the 30 Gy group ( all P < 0. 05 ) . Conclusion 30 Gy is the best radiation dosage by the linear accelerator radiated. SOD activity decrease, MAD and ROS levels increase in SD rats after modeled. These changes may be the basis of radiation retinopathy.